Method and apparatus for improved gas mask and filter test penetrometer

Abstract

An accurate, instantaneous determination of geometric standard deviation gma.g of particle size distribution of aerosols, permitting verification that the test aerosols fall within suitable specifications and are giving test results that are truly representative of the degree of protection from smoke and aerosols that representative mask filters and filter media afford under actual use conditions. Provided herein is a more precise means of measuring aerosol penetration of gas masks. Determination of geometric standard deviation includes the steps of transmitting focused and coherent or optically filtered light from a source to a chamber containing an aerosol sample and then detecting and comparing the intensity of polarized light scattered at a first angle relative to said light source to the intensity of polarized light scattered at a second angle relative to said light source. Angles are selected to optimize signal-to-noise of the instrument, not as historically done to optimize ratios of one signal to the other as determined by calculation but whose measurement angles do not correspond to maximum strengths of the individual signals. The first and second detector angles as determined by this new method can by selected by manual adjustment of a pivoted detector, or by two or more detectors permanently affixed at two or more preselected angles, or automatically to compensate for changes in particle size when test aerosols of a constant size connot be continuously generated.